Metal sealant containing amino acrylic ester



United States Patent Oflice 3,493,552 METAL SEALANT CONTAINING AMINO ACRYLIC ESTER Charanjit Rai, Somerset, N..I., and William James Keillor,

Westchestcr, Ill., assignors to Broadview Chemical Corporation, a corporation of Illinois No Drawing. Continuation-in-part of application Ser. No. 561,381, June 29, 1966. This application Mar. 24, 1969, Ser. No. 809,986

Int. Cl. C081? 3/64 US. Cl. 260-895 7 Claims ABSTRACT OF THE DISCLOSURE An alkylaminoalkyl alcohol ester of an acrylic acid is used as a room temperature curing monomer in a shelf stable fast curing sealant composition which contains a hydroperoxide catalyst and cures when placed between facing ferrous metal surfaces.

RELATION TO THE CO-PENDING APPLICATIONS This application is a continuation-in-part of my copending application Ser. No. 561,381 entitled Metal Sealant Containing Amino Acrylic Ester filed June 29, 1966, and now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to sealants containing a liquid monomer and a catalyst. The sealants are shelf stable but are capable of setting up at room temperature when placed between closely facing ferrous metal surfaces.

Prior art Sealant compositions are liquid solventless adhesives usually used for adhering metal surfaces to each other. They can be put to a variety of specific uses such as for adhering a nut to a bolt, mounting a bearing, adhering metal slip fits, abutting joints and threaded joints such as on pipes and pipe fittings. They are shelf stable under normal storage conditions but are triggered to set up or polymerize by placing them between closely metal surfaces. Heretofore commercial sealants have used as the basic monomer a diacrylic ester of a polyethylene glycol or the like.

During the prosecution of the above identified copending application, Graves US. 2,138,763, has been considered as a prior art reference. Graves teaches the preparation of a number of kinds of amino alcohol esters of methacrylic acid and their polymerization in solution by exposure of solutions of the ester to ultraviolet light or by heating with polymerization cataylsts such as benzoyl peroxide. The polymerization is slow because of inhibition by the amino group. Although Graves incidentally suggests use of the resulting polymer in adhesive applications, the polymer is not suitable as a room temperature setting adhesive.

Further, attempts have been made to provide sealant compositions from a variety of different monomers with little or no success. For example, methylmethacrylate, which is one of the more common acrylic monomers, is not a room temperature reactive monomer. This holds true for almost all other monomers. In order to try to activate such monomers, accelerators have been used but these have been found to either render the composition unstable or else they do not have the desired accelerator effect.

The one successful commercial system which has used the diacrylate of polyethylene glycol or the like as the monomer is a shelf stable sealant composition. Such shelf 3,493,552 Patented Feb. 3, 1970 stable sealant compositions are provided in a full range of varying strengths, viscosity, thixotropy and curing or setting rates. The range of products can include very fast curing sealants of various ultimate strengths as well as slower curing materials also of various ultimate strengths. Such sealant compositions usually include an acrylic monomer which is capable of being cured at room temperature within the desired period of time.

SUMMARY OF THE INVENTION This invention provides a sealant composition which uses an acrylic ester of an alkylaminoalkyl alcohol as a room temperature setting monomer containing a hydroperoxide catalyst, which can be either an organic hydroperoxide or hydrogen peroxide, for setting the monomer up. The monomer itself functions as the solvent for any soluble ingredients in the sealant, so significant amounts of volatile solvent are not used and there is no need for removal of volatile solvents to produce a bond.

It is an object of this invention to provide new and useful liquid sealant compositions which will set up at room temperature in contact with closely facing metal surfaces within a reasonable time to provide a good bond between the surfaces.

Another object of this invention is to provide a high strength sealant composition which has good stability and an acceptable or desired rate of room temperature cure.

A still further object of this invention is to provide a new and useful sealant composition employing a highly advantageous room temperature reactive or curing mono mer system.

Other objects of this invention will be apparant from the descriptions given herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Briefly, the present invention involves the use of an acrylic ester of an alkylaminoalkyl alcohol as a room temperature reactive monomer in a sealant composition. Especially useful esters have the following formula:

wherein x is an integer 0 to 5, inclusive, y is an integer 1 to 6, inclusive, and R is hydrogen or C to C alkyl. The nature of the R group of the acrylic portion of the ester is unimportant. For example, R can be hydrogen, halogen, hydroxy, cyano, or substituted or unsubstituted saturated or unsaturated hydrocarbon. Preferably, R is hydrogen, halogen or lower alkyl, i.e. C to C because of the more ready availability of such acrylic acids and/ or their alkylaminoalkyl alcohol esters. The halogens are chlorine, iodine, fluorine and bromine.

.To prepare the present sealant compositions, it is merely necessary to mix a suitable amount of hydroperoxide catalyst with the sealant monomer, including the acrylic ester of an alkylaminoalkyl alcohol. Metal containers should not be used because of the chance of premature polymerization. It has been found that the hyperoxide catalyst, e.g. organic hydroperoxide can usually be used alone, eg in amounts of .1 to 15% or more, and preferably 1 to 8%, in the sealant composition to cause the ester to set up within a reasonable period of time, e.g. less than 6 hours and preferably less than 3 or 4 hours, at room temperature (70 F.), when the composition is used as a sealant. Examples of suitable organic hydroperoxide are cumene hydroperoxide, t-butyl hydroperoxide, methylethylketone hydroperoxide, tetralin hydroperoxide, 2,5-dimethylhexyl-2,S-dihydroperoxide, and the like.

3 4 More specifically, the room temperature reactive monomethylmethacrylate and other soluble acrylic polymers mers of the present sealants include, but are not limited can also be included. The soluble polymers and prepolyto, the following: butylaminoethyl methacrylate, dimethyl mers can be used to increase the viscosity of the sealant aminoethyl cyanoacrylate or methacrylate or chloroacrycomposition and will often impart higher strength charlate, dihexyl aminomethyl acrylate, amylaminoethyl ethacteristics to the sealant. acrylate, di(t-butyl) aninoethyl methacrylate, di(t-butyl) Inhibitors or stabilizers can be added as needed to balaminohexyl methacrylate, hexylaminohexyl pentacrylate, ance or prevent instability of the sealant. Hydroquinone methylaminomethyl methacrylate, as Well as other est s is a preferred inhibitor and stabilizer because of its availof acrylic acids and alkylaminoalkanols. ability and effectiveness. Hydroquinone, in a total amount The present monomers may be used in mixtures with of 20 to 2000 p.p.m., more usually 60 to 600 p.p.m., will other monomers, including other room temperature reprobably be sufficient to stabilize most sealant composi active acrylic monomers such as an acrylic poly-ester, e.g. tions containing the ester. Other conventional inhibitors di-, tri-, and tetra-, esters of a polyol, e.g. polyethylene or stabilizers for inhibiting polymerization of vinyl comglycol as described by L. W. Kalinowski in US. Patent pounds can be used as will be apparent to those in the art. No. 3,249,656. Other copolymerizable acrylic monomers In an advantageous form of the present invention, polymay also be used in the mixtures, which monomers are merization or cure rate accelerators can be included in not truly room temperature reacting by themselves, e.g. the compositions, e.g. in amounts of .001 to 10% by weight acrylic ester methyl metharcylate, butyl methacrylate, and preferably 0.01 to 5% by weight based on total monohydroxyethylmethacrylate or acrylate, etc. The disclosures mer in the sealant composition. Useful accelerators for of monomers and hydroperoxide catalysts and the specific stable compositions include such nitrogen-containing comexamples of such monomers and catalysts described in the pounds as the alkoxy alkyl amines, alkylaminoalkyl above-identified patent are hereby incorporated in this amines, primary and secondary alkyl amines, cycloalkyl application by reference as examples of catalysts which amines, and primary allylic amines. Other compounds are useful in the present sealants and monomers which which may be useful accelerators are alkylol amines, can be mixed therewith, if desired. tertiary amines, organic amides, organic imides, ureas and It is intended that other monomers and even polymeric cyclic ureas, pseudo-thioureas, heterocyclic compounds materials can also be included in the sealant compositions. containing nitrog n in the heterocyclic ring trialkylol Such other monomers can be those which are not readily amino compounds, amino acids, etc. In a preferred form initiated at room temperature and can be included to of the present invention, an organic sulfimide, amide, impart various desirable properties, e.g. for the purpose imide or the like is used as a cocatalyst to further inof varying the strength of the sealant. Such other monO- crease cured strength of the bond. The cocatalyst funcmers include generally the vinylic monomers and espections to provide a more complete cure. ially other acrylic monomers such as acrylic acid esters The following examples are offered for the purpose of of monoand polyhydric alcohols. Additionally, allylic illustration of the invention and are not intended as limmonomers such as allyl alcohol, allyl methacrylate and iting. In each example the recited ingredients were mixed diallyl phthalate can be used, although some of these in a small polyethylene bottle, and the bottle was then monomers are lacrimatious and it is preferred not to inplugged with a dispenser cap having a drop-dispensing clude them in large portions where the sealant is to be spout. The ingredients were mixed by shaking until a used in an unventilated area. Such vinyl monomers as good solution was formed.

divinylbenzene, styrene and alphamethyl styrene can also be used, although these tend to seep through contain- EXAMPLES 1 To 23 ers, especially polyethylene containers, so a more imper- In each example reported in the table below, the invious container should be selected for the product. Polygredients indicated were mixed with the accelerator or men'c materials and prepolymers soluble in the monomers cocatalyst and catalyst being added seriatim as the last can also be used to advantage; for example, the solid preingredients. The Master Batch contained 73.7% by polymer of diallyl phthalate marketed under the tradeweight polyethylene glycol dimethacrylate (averaging name Dapon-35. Soluble polyesters and especially the tetraethylene glycol dimethacrylate), 26.3% by weight liquid, including viscous, polyesters of a polyol such as diallyl phthalate prepolymer (solid prepolymer marketed diethylene glycol with fumaric or maleic acid, as well as under the name Dapon-35) and 0.0001% hydroquinone. such polyesters modified by the substitution of phthalic The catalysts and cocatalysts are identified in the table and or other plyfunctional acids for part of the maleic and/ or were used in amounts of about 2.5% and 0.3%, respecfumaric acid can also be used to advantage. Soluble polytively unless otherwise indicated.

AMOUNTS OF INGREDIENTS IN EACH EXAMPLE EXAMPLE Ingredients (percent) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Master Batch 1 Dimethylamlnoethyl methacrylate 1 Cyclohexyl methacrylate l 50 50 50 50 50 50 50 50 50 Tetrahydroiurl'uryl methacrylate 1 50 50 50 50 50 Polyethylene Glycol dimethacrylate 50 50 50 n-Butyl methacrylate 1 Ethylene glycol dimethacrylate 1 Acrylic acid C atalysts:

Cumene hydrop eroxide t-Butyl hydroperoxide Cocatalysts:

Benzoic sulfimlde r. X X X X Triallyl cyanurate N, N-dimethyl formamlde Accelerators:

N, N-dlmethyl aniline 1% N, N-dimethyl triethylene Glycol diamine Diisopropyl amine. N-ethyl morphollne N-aminopropyl morpholine t-Butylamlne Allyl amine Ethylene glycol diamine XXXX X XXXXXXXXXXXXXXXXXX.

1 Amounts given as parts by weight.

The above examples were tested for initial cure time at room temperature, 24 hour room temperature bond strength, and shelf life' or stability by the following procedures with the results reported in the table below:

Initial cure to finger tight: 3 small drops of each formulation were dispensed on the exposed threads of each of a plurality of degreased %24, 1 inch medium carbon steel cap screws on each of which a degreased medium carbon steel nut had been threaded up close to the cap screw head. The nut was then backed off until it was within the area of threads to which the formulation had been applied. Each cap screw was then placed head down on a level surface and allowed to stand. A separate cap screw for each formulation was checked after expiration of a different preselected time interval; and when a nut was found to be finger tight, i.e. the nut could not be manually turned relative to the cap screw without the aid of a wrench or other tool, the time was recorded.

24-hour room temperature cured bondstrength: 24 hours after treatment of a cap screw with the sealant or above the head of the cap screw was held in a vise with the shank of the cap screw disposed vertically. A torque wrench was applied to the nut, and the torque required to dislodge the nut was noted.

Stability: Each composition, in its polyethylene bottle, was aged in an oven maintained at about 81 to 82 C. for 90 minutes. If the composition gelled, this was noted. The absence of gelling indicates at least about 23 years shelf life for the composition at ambient temperatures.

TEST RESULTS Time to Finger Torque, 24 hours, Stability at Example Tight, min. in. lb. 82 C. (min) 2 Not previously checked. 3 Not availableno test made. 4 Gelled at 90 min.

The temperature conditions during the preparation and testing of all sealant compositions herein were in the range of about 70 F. to 75 F.

EXAMPLE 24 Di-methylaminoethyl methacrylate containing 2% by weight t-butyl hydroperoxide.

EXAMPLE 2S Di-methylaminoethyl methacrylate containing 2% by weight cumene hydroperoxide.

EXAMPLE 26 A commercial type formulation containing 100 parts by weight di-methylaminoethyl methacrylate, about .02 part by weight hydroquinone, 0.3 part by weight benzoic sulfimide, 0.5 part by weight t-butyl hydroperoxide, .05 part by weight metabromotrifiuro toluene and .025 part by weight ethoxyethoxyethoxypropylamine.

A small amount of each of Examples 24 through 26 was applied to a separate set of steel bolts and then a steel nut was threaded over the thread of each bolt. Each nut and bolt combination was placed on a support surface, nut end up. Nuts were tested periodically for finger tightness, and it was found that Example 24 was finger tight in 210 minutes and each of Examples 25 and 26 were finger tight in 300 minutes.

At the end of 24 hours, a torque wrench was applied to the nut of the nut and bolt combination secured by each of Examples 24 through 26 and the torque required to loosen the nut was recorded. Examples 24, 25 and 26 required inch lbs., 166 inch lbs., and inch lbs., respectively, to loosen the nut and bolt.

Compositions were also prepared using di-t-butyl diperphthalate and t-butyl peracetate as catalysts in lieu of the hydroperoxides. Although these compositions performed adequately for some purposes, they were not of the preferred type. Some further examples were prepared using the dimethylaminoethyl methacrylate monomer with the commonly used peroxide catalyst benzoyl peroxide and the formulations were completely unacceptable for use as sealant compositions.

In still further examples, the procedures of the above examples are repeated substituting the following monomers for the dimethylaminoethyl methacrylate: dimethylaminoethyl ethacrylate, chloroacrylate or acrylate, methylaminoethyl methacrylate, cyclohexyl aminoethyl methacrylate, chloroacrylate, diisohexylaminoethyl ethacrylate, dihexylaminopropyl methacrylate, oleylaminoethyl, butylaminoethyl methacrylate or the like. In each case, the stability, 24-hour torque properties and room temperature cure time to finger tight are acceptable for many sealant uses.

All percentages given herein are percentages by weight unless otherwise indicated.

The foregoing detailed description is given for clearness of understanding only and no unnecessary limitations are to be understood therefrom, as some modifications will be obvious to those skilled in the art.

We claim:

1. A liquid sealant composition which is capable of storage as a liquid at room temperature but which sets up to an adherent solid polymer bond when contacted with and confined between closely facing metal surfaces at room temperature, said composition having a polymerizeable room temperature reactive acrylic monomer as said liquid consisting essentially of an acrylic ester of an alkylaminoalkyl alcohol and an amount of a catalyst system consisting essentially of t-butyl hydroperoxide maintaining said sealent in a normal stable liquid condition, but sufficient to set said monomer up as a solid polymer adhering to and filling the space between said surfaces within a period of a few hours in response to contact of the composition between said surfaces, wherein said acrylic ester has the formula:

wherein x is an integer 0 to 5, inclusive, y is an integer 1 to 6, inclusive, R is selected from the class consisting of hydrogen, halogen, hydroxy, cyano, and lower alkyl, and R is selected from the class consisting of hydrogen and C to C alkyl.

2. The composition of claim 1 wherein said acrylic ester is dimethyl aminoethyl methacrylate.

3. The composition of claim 1 wherein said acrylic ester is butylaminoethyl methacrylate.

4. The composition of claim 1 including an accelerator for accelerating polymerization by said catalyst.

5. A laminate structure comprising separate members having closely facing ferrous metal surfaces and a layer of the composition of claim 1 set between said surfaces and securing said members as a unit.

6. A method of adhering closely facing metal surfaces, which method comprises interposing between said surfaces the liquid composition of claim 1 and permitting said surfaces to stand at ambient conditions until said composition is set.

8 References Cited UNITED STATES PATENTS 11/1938 Graves.

5/1966 Kalinowski 260-861 HARRY WONG, 1a., Primary Examiner US. Cl. X.R.

7 The method of claim 6 wherein said liquid composi- 10 117-432; 161218; 204-159.22; 26078.5, 80.81,

tion sets up in less than about six hours. 

